Since the beginning of the 21st century, cloud computing, big data and artificial intelligence have swept the world. The explosive growth of information has made stable communication with low delay, high speed, large capacity, easy to access become the development trend. However, the existing medium and low frequency spectrum resources are tight and the frequency band is crowded, which is not enough to meet the needs of communication. The high frequency band, especially the millimeter wave band, is rich in spectrum resources and meets the needs of a high signal transmission rate. Therefore, the working frequency of the signal is developing towards high frequency microwave or even millimeter wave band. Due to the "rate bottleneck" of electronic devices, it is difficult to generate and transmit high-frequency millimeter wave signals based on traditional electrical methods. The development of microwave photonics provides a new way for the generation, processing and transmission of high-frequency millimeter wave signals. Combining the advantages of optical fiber communication and wireless communication, the radio over fiber (ROF) technology provides great convenience for mass access and wireless transmission at present, and has broad application prospects. High frequency factor millimeter-wave technology based on external modulator is one of the most promising millimeter-wave generation technologies, in the field of microwave photonics, which can realize the transformation from low frequency RF driving signal to high frequency millimeter-wave signal. In order to improve the frequency doubling coefficient and reduce the complexity of the system of the millimeter-wave signal generation in the radio over fiber, a 24-frequency millimeter wave optical wireless communication system based on the combination of cascaded dual-drive Mach Zehnder modulator (DMZM) and high nonlinear fiber (HNLF) is proposed. By adjusting the parameters, the two modulators work at the maximum biaspoint to generate the fourth-order optical sideband with pure spectrum. The data signal is loaded into the 4-order optical sideband by means of single-sideband modulation, and then the two sides are coupled and transmitted. The 12-order optical sideband is obtained by the four-wave mixing effect of HNLF and the filtering of the cross multiplexer. Finally, the high quality 24-tupling millimeter-wave signal is generated by photodetector (PD) beat frequency. In addition, the working principle of the system is analyzed in detail, and the influence of the length of HNLF, the incoming optical power and the standard linear optical fiber on the system performance is verified by simulation. The simulation results show that when the system is in error-free transmission, the power cost of back-to-back (BTB) transmission and 30 km fiber transmission is 2.5 dB. This scheme has the advantages of a simple structure, high frequency doubling coefficient, insensitive polarization and good performance. In addition, it avoids the use of active device SOA, further reduces the experimental cost and improves the system efficiency, which provides a theoretical reference for the actual construction of ROF system, and provides a new way for the development of microwave photonics.